Hubble detects 'water plumes' on surface of Europa

NASA has published images of what may be water vapour plumes erupting off the surface of Jupiter's icy moon Europa.

Using the Hubble Space Telescope, astronomers detected activity in the south pole of Europa, which is thought to house a huge global ocean containing twice as much water as all the oceans on Earth.

The ocean is believed to be protected by a thick ice layer and the plumes could mean missions to Europa may be able to gather samples from the waters without having to drill though the ice.

The plumes are estimated to rise about 125m before raining back onto Europa's surface and were observed by a team initially attempting to discover more about Europa's atmosphere.

Led by William Sparks of the Space Telescope Science Institute (STScI), the team discovered the same method used to detect atmospheres around planets orbiting other stars, could also be used to observe any water vapour venting from Europa's surface.

"The atmosphere of an extrasolar planet blocks some of the starlight that is behind it," Dr Sparks explained.

"If there is a thin atmosphere around Europa, it has the potential to block some of the light of Jupiter, and we could see it as a silhouette. And so we were looking for absorption features around the limb of Europa as it transited the smooth face of Jupiter."

Over 15 months the team observed Europa passing in front of Jupiter in 10 separate occurrences. On three of these occasions they saw what could be plumes.

The finding supports evidence from 2012, when a team of astronomers detected evidence of water vapour erupting from Europa's south pole more than 100 miles into space.

Although both teams detected evidence of water vapour on Europa using the Hubble's Space Telescope Imaging Spectrograph instrument, they each used entirely independent methods.

"When we calculate in a completely different way the amount of material that would be needed to create these absorption features, it's pretty similar to what Roth and his team found," Dr Sparks said.

"The estimates for the mass are similar, the estimates for the height of the plumes are similar. The latitude of two of the plume candidates we see corresponds to their earlier work."

However, the two teams have not been able to simultaneously detect the plumes using their respective methods, suggesting the plumes may only erupt sporadically.

If the findings are confirmed, Europa will be the second moon in the solar system known to have water vapour plumes. Saturn's moon Enceladus was the first known to produce such jets of water when they were discovered spewing off its surface in 2005.

Scientists may now go on to use NASA's James Webb Space Telescope, scheduled to launch in 2018, to confirm the activity, which uses infrared technology.

NASA is also planning a mission to Europa that could confirm the presence of plumes.

"Hubble's unique capabilities enabled it to capture these plumes, once again demonstrating Hubble's ability to make observations it was never designed to make," said Paul Hertz, director of the Astrophysics Division at NASA Headquarters in Washington.

"This observation opens up a world of possibilities, and we look forward to future missions - such as the James Webb Space Telescope - to follow up on this exciting discovery."

"Europa's ocean is considered to be one of the most promising places that could potentially harbor life in the solar system," said Geoff Yoder, acting associate administrator for NASA's Science Mission Directorate in Washington.

"These plumes, if they do indeed exist, may provide another way to sample Europa's subsurface."